Heretofore, when stenosis occurs in a vessel of a living body, such as a coronary artery, percutaneous transluminal angioplasty (PTA) is performed in which the stenosed portion in the vessel is expanded to improve the blood flow using a medical balloon catheter.
The site once stenosed, however, is known to have high possibility of restenosis or acute occlusion due to intimal dissection even after PTA. To prevent such acute occlusion or restenosis, a tubular shaped stent is implanted at the site following PTA. The stent is in a contracted state when introduced into a blood vessel, and subsequently expanded in diameter so as to be deployed at the intended site scaffolding the vessel wall from its inside.
The stent to be implanted in a blood vessel is inserted and transported to the intended site in the vessel by using a catheter having a balloon which can be dilated with expansion medium supplied thereto. Specifically, the contracted stent is mounted onto the balloon provided at the distal portion of the catheter to be inserted into the blood vessel and transported to the intended site together with the balloon. With the balloon inflation by supplying the expansion medium into it, the stent is expanded in diameter, and consequently deployed at the intended site. The once expanded stent keeps its expanded state even after the balloon is deflated by removal of the expansion medium, thereby scaffolding the implanted site radially to allow fluid path for humor such as blood in the vessel lumen.
The stent is formed into cylindrical shape such that a fluid path is configured through its one end to the other. This stent is contracted to be mounted onto a contracted balloon, and introduced into the blood vessel together with the balloon. Being an independent cylindrical body mounted onto the balloon, however, the stent may be dislocated on the balloon or dislodged from it under force such as friction during delivery. The dislodged stent cannot be expanded by inflating the balloon, resulting in failure to deploy it at the intended site. The stent not dislodged from the balloon but just dislocated relative to the balloon may be subject to the balloon inflation force unequally along its entire length, resulting in its unequal expansion along its entire length. The stent expanded unequally along its length cannot scaffold the vessel wall in the vessel as intended.
In order to prevent dislocation or dislodgement of the stent mounted on the balloon, the present inventor has proposed a catheter apparatus for delivery of a stent wherein a balloon catheter, having a balloon on which the stent is mounted, is inserted into a protective sheath (Patent Document 1). Furthermore, in this catheter apparatus, a holding member holds the one end of the stent to prevent stent dislocation relative to the balloon, when the stent is extruded from the protective sheath to expand in diameter. Since, in this catheter apparatus, the stent mounted on the balloon attached to the distal end of the catheter is covered by the protective sheath when delivered within a vessel such as a blood vessel, stent dislodgement from the balloon can be surely prevented.